The present invention relates to a roll-over valve which prevents leakage of fuel from a motor vehicle fuel tank through a vent line when the automobile is tilted in excess of a predetermined angle or has been tilted and is upside down.
In order to minimize the evaporative loss of fuel to the atmosphere from motor vehicle fuel tanks, a vent line is typically attached to the tank for directing fuel vapors to storage containers such as to the fuel cannister and/or to the engine such as the intake manifold. Such vent lines may be susceptible to fuel leakage from the fuel tank in the event of an accidental roll-over of the automobile or even when the automobile is tilted to an extreme angle such as may occur if an automobile runs off the road over an embankment or into a ditch. Fuel leakage is to be avoided, if possible. Thus, it has been common to include a positionally sensitive roll-over valve in the vent line to close it when the automobile has been tilted in excess of a predetermined angle or has rolled over and is upside down. The closed valve prevents leakage of fuel from the tank through the vent lines and thus minimizes the possibility of a fire hazard which may result therefrom.
U.S. Pat. No. 4,095,609 issued to Martin on Jan. 20, 1978 discloses a roll-over valve. This known roll-over valve includes a heavy ball resting on a conical seat inside a valve body chamber. The valve body chamber includes an inlet connected to the fuel tank and an upper outlet disposed immediately above the ball. A movable cage encloses the ball between top and bottom members so as to move with it as the valve is inclined from an upright position and the ball tends to roll up the conical surface on which it rests, thus moving the cage upwardly. The top member of the cage is adapted to close an opening through which the outlet communicates with the valve chamber when this occurs. When the valve is returned to its normal upright position and the ball returns to its center of the seat, the ball urges the cage by pressing its bottom member downwardly, thus positively opening the outlet.
Since the top of the cage closes the outlet opening and the inlet always communicates with the valve body chamber, liquid fuel from the fuel tank may enter the valve body chamber through the vent line when the vehicle carrying the valve is inclined to an angle which is considered abnormal such as when the automobile has rolled over and is upside down. Thus, foreign matters contained in liquid fuel may form deposits on top of the cage member and conical surface. Deposits formed on them increase the possibility that the outlet opening is not completely closed by the top cage member when the ball rolls up the conical surface. In order to ensure good response upon the actuation of the cage as the ball rolls up or down the conical surface, the bottom member of the cage takes the form of a light weight structure such as a rail. Thus, there is the possibility that the bottom member may be broken upon receiving an impact by the ball when the valve is subject to a great acceleration. If the bottom cross member is broken, the top cage member may continue to close the outlet opening once it has been urged to move toward the outlet opening by the ball. This is because the known roll-over valve reacts positively to open itself by contacting the ball to the bottom cross member of the cage.
An object of the present invention is to provide an improved roll-over valve which does not allow the entry of liquid fuel into the valve body chamber and which is free from the problem that the valve stays undesirably closed.